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  • LM397 Single General-Purpose Voltage Comparator

    • SNOS977F May   2001  – May 2016 LM397

      PRODUCTION DATA.  

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  • LM397 Single General-Purpose Voltage Comparator
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input Stage
      2. 7.3.2 Output Stage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Hysteresis
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input Voltage Range
        2. 8.2.2.2 Minimum Overdrive Voltage
        3. 8.2.2.3 Output and Drive Current
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. IMPORTANT NOTICE

Package Options

Mechanical Data (Package|Pins)
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    • MPDS018T
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DATA SHEET

LM397 Single General-Purpose Voltage Comparator

1 Features

  • TA = 25°C. Typical Values Unless Otherwise Specified.
  • 5-Pin SOT-23 Package
  • Industrial Operating Range −40°C to +85°C
  • Single or Dual Power Supplies
  • Wide Supply Voltage Range 5 V to 30 V
  • Low Supply Current 300 µA
  • Low Input Bias Current 7 nA
  • Low Input Offset Current ±1 nA
  • Low Input Offset Voltage ±2 mV
  • Response Time 440 ns (50-mV Overdrive)
  • Input Common-Mode Voltage 0 to VS – 1.5 V

2 Applications

  • A/D Converters
  • Pulse, Square-Wave Generators
  • Peak Detector
  • Industrial Applications

3 Description

The LM397 device is a single voltage comparator with an input common mode that includes ground. The LM397 is designed to operate from a single 5-V to 30-V power supply or a split power supply. Its low supply current is virtually independent of the magnitude of the supply voltage.

The LM397 features an open-collector output stage. This allows the connection of an external resistor at the output. The output can directly interface with TTL, CMOS and other logic levels, by tying the resistor to different voltage levels (level translator).

The LM397 is available in the space-saving 5-Pin SOT-23 package and is pin-compatible to TI’s TL331, a single differential comparator.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
LM397 SOT-23 (5) 2.90 mm × 1.60 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Circuit

LM397 20022109.gif

4 Revision History

Changes from E Revision (October 2015) to F Revision

  • Changed incorrect Pin Functions table entries. Pins 4 and 5 were swapped.Go

Changes from D Revision (March 2013) to E Revision

  • Added ESD Rating table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section. Go

Changes from C Revision (March 2013) to D Revision

  • Changed layout of National Data Sheet to TI formatGo

5 Pin Configuration and Functions

DBV Package
5-Pin SOT-23
Top View
LM397 20022108.gif

Pin Functions

PIN TYPE DESCRIPTION
NAME NO.
GND 2 P Ground
OUTPUT 4 O Output
VIN+ 3 I Noninverting Input
VIN– 1 I Inverting Input
VS 5 P Supply

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
VIN differential 30 30 V
Supply voltages ±15 30 V
Voltage at input pins −0.3 30 V
Junction temperature(3) 150 ºC
Soldering information    Infrared or Convection (20 sec.) 235 ºC
Wave Soldering (10 sec.) 260 ºC
Storage Temperature, Tstg −65 150 ºC
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
(3) The maximum power dissipation is a function of TJ(MAX), RθJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ RθJA . All numbers apply for packages soldered directly onto a PCB.

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(2)    ±2000 V
Machine Model(1)(2)  ±200
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC) Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).

6.3 Recommended Operating Conditions

MIN MAX UNIT
Supply voltage, VS 5 30 V
Temperature(1) −40 85 °C
(1) The maximum power dissipation is a function of TJ(MAX), RθJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ RθJA . All numbers apply for packages soldered directly onto a PCB.

6.4 Thermal Information

THERMAL METRIC(1) LM397 UNIT
DBV (SOT-23)
5 PINS
RθJA Junction-to-ambient thermal resistance(2) 186 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 92.8 °C/W
RθJB Junction-to-board thermal resistance 38.9 °C/W
ψJT Junction-to-top characterization parameter 5.6 °C/W
ψJB Junction-to-board characterization parameter 38.4 °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.
(2) The maximum power dissipation is a function of TJ(MAX), RθJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ RθJA . All numbers apply for packages soldered directly onto a PCB.

6.5 Electrical Characteristics

Unless otherwise specified, all limits are ensured for TA = 25°C, VS = 5 V, V− = 0 V, VCM = V+/2 = VO.
PARAMETER TEST CONDITIONS MIN(2) TYP(1) MAX(2) UNIT
VOS Input offset voltage VS = 5 V to 30 V,
VO = 1.4 V, VCM = 0 V		 TA = 25ºC 2 7 mV
At the temperature extremes 10
IOS Input offset current VO = 1.4 V, VCM = 0 V TA = 25ºC 1.6 50 nA
At the temperature extremes 250
IB Input bias current VO = 1.4 V, VCM = 0 V TA = 25ºC 10 250 nA
At the temperature extremes 400
IS Supply current RL = open, VS = 5 V 0.25 0.7 mA
RL = open, VS = 30 V 0.3 2
IO Output sink current VIN+ = 1 V, VIN− = 0 V, VO = 1.5 V 6 13 mA
ILEAKAGE Output leakage current VIN+ = 1 V, VIN− = 0 V, VO = 5 V 0.1 nA
VIN+ = 1 V, VIN− = 0 V, VO = 30 V 1 µA
VOL Output voltage low IO = −4 mA, VIN+ = 0 V,
VIN− = 1 V		 TA = 25ºC 180 400 mV
At the temperature extremes 700
VCM Common-mode input voltage range VS = 5 V to 30 V(3) TA = 25ºC 0 VS – 1.5 V
At the temperature extremes 0 VS – 2
AV Voltage gain VS = 15 V, VO = 1.4 V to 11.4 V,
RL > = 15 kΩ connected to VS		 120 V/mV
tPHL Propagation delay
(high to low)		 Input overdrive = 5 mV
RL = 5.1 kΩ connected to 5 V, CL = 15 pF		 900 ns
Input overdrive = 50 mV
RL = 5.1 kΩ connected to 5 V, CL = 15 pF		 250
tPLH Propagation delay
(low to high)		 Input Overdrive = 5 mV
RL = 5.1 kΩ connected to 5 V, CL = 15 pF		 940 µs
Input overdrive = 50 mV
RL = 5.1 kΩ connected to 5 V, CL = 15 pF		 440 ns
(1) Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not specified on shipped production material.
(2) All limits are specified by testing or statistical analysis.
(3) The input common-mode voltage of either input should not be permitted to go below the negative rail by more than 0.3V. The upper end of the common-mode voltage range is VS – 1.5 V at 25°C.

6.6 Typical Characteristics

TA = 25°C. Unless otherwise specified.
LM397 20022103.gif Figure 1. Supply Current vs Supply Voltage
LM397 20022104.gif Figure 3. Output Saturation Voltage vs Output Sink Current
LM397 20022101.gif Figure 2. Input Bias Current vs Supply Current
LM397 20022102.gif Figure 4. Input Offset Voltage vs Supply Voltage

7 Detailed Description

7.1 Overview

A comparator is often used to convert an analog signal to a digital signal. The comparator compares an input voltage (VIN) at the noninverting pin to the reference voltage (VREF) at the inverting pin. If VIN is less than VREF the output (VO) is low (VOL). However, if VIN is greater than VREF, the output voltage (VO) is high (VOH). Refer to Figure 6.

LM397 20022110.gif Figure 5. Basic Comparator
LM397 20022111.gif Figure 6. Basic Comparator Output

7.2 Functional Block Diagram

LM397 functional_diagram_snos977.gif

7.3 Feature Description

7.3.1 Input Stage

The LM397 has a bipolar input stage. The input common-mode voltage range is from 0 to (VS – 1.5 V).

7.3.2 Output Stage

The LM397 has an open-collector grounded-emitter NPN output transistor for the output stage. This requires an external pullup resistor connected between the positive supply voltage and the output. The external pullup resistor should be high enough resistance so to avoid excessive power dissipation. In addition, the pullup resistor should be low enough resistance to enable the comparator to switch with the load circuitry connected. Because it is an open-collector output stage, several comparator outputs can be connected together to create an OR’ing function output. With an open collector, the output can be used as a simple SPST switch to ground. The amount of current which the output can sink is approximately 10 mA. When the maximum current limit is reached, the output transistor will saturate and the output will rise rapidly (Figure 7).

LM397 20022107.gif Figure 7. Output Saturation Voltage vs Output Sink Current

7.4 Device Functional Modes

7.4.1 Hysteresis

The basic comparator configuration may oscillate or produce a noisy output if the applied differential input is near the input offset voltage of the comparator. This tends to occur when the voltage on the input is equal or very close to the other input voltage. Adding hysteresis can prevent this problem. Hysteresis creates two switching thresholds (one for the rising input voltage and the other for the falling input voltage). Hysteresis is the voltage difference between the two switching thresholds. When both inputs are nearly equal, hysteresis causes one input to effectively move quickly pass the other. Thus, effectively moving the input out of region that oscillation may occur.

For an inverting configured comparator, hysteresis can be added with a three resistor network and positive feedback. When input voltage (VIN) at the inverting node is less than non-inverting node (VT), the output is high. The equivalent circuit for the three resistor network is R1 in parallel with R3 and in series with R2. The lower threshold voltage VT1 is calculated by Equation 1:

Equation 1. VT1 = ((VS R2) / (((R1 R3) / (R1 + R3)) + R2))

When VIN is greater than VT, the output voltage is low. The equivalent circuit for the three resistor network is R2 in parallel with R3 and in series with R1. The upper threshold voltage VT2 is calculated by Equation 2:

Equation 2. VT2 = VS ((R2 R3) / (R2 + R3)) / (R1 + ((R2 R3) / (R2 + R3)))

The hysteresis is defined in Equation 3:

Equation 3. ΔVIN =  VT1 – VT2
LM397 20022113.gif Figure 8. Inverting Configured Comparator - LM397

 
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